Necessity has historically been the mother of conscription; when we feel sufficiently threatened, we'll have a draft. While I'm not philosophically opposed to drafting women (for support functions) we learned in WWII that private industry can use the labor pool of women left behind for war production; i.e., Rosie the Riveter.
The nation would maintain a pool of men with basic training who would provide the bodies necessary in wartime. With all men having an experience of the military and having finished the basic training there would not be that fear of the unknown that is the source of most of the resistance by young men to the military. When the country is at war the rate of enlistment will be much higher simply because military service is not alien. No exceptions (except medical and sexual) would make it a normal part of life, not something to be avoided at all costs.